What Causes Rain In The Driest Place On Earth? New Study Gives Answers

New study by researchers from American Geophysical Union explains atmospheric mechanisms behind the wettest of the precipitation events in Atacama Desert that receives an average 5mm rainfall/year.

The Atacama Desert in Northern Chile, commonly known as the driest place on Earth (Photo: Getty)

New Delhi: The Atacama Desert in northern Chile, commonly known as the driest place on Earth, receives an average rainfall as low as five millimetres per year. Rare rain events can come swiftly and intensely in the enduring dryness.

These rain events shape the landscape and provide precious moisture to plants and species. These species have adapted to extended dry spells or harvesting coastal fog. 

A new study conducted by researchers from the American Geophysical Union in the United States explains the atmospheric mechanisms behind the wettest of these precipitation events. The study was recently published in the journal, Geophysical Research Letters.

Role Of Moisture Conveyor Belts In Causing Rainfall In The Atacama Desert

It is believed that certain moisture conveyor belts are responsible for intense rain events in the Atacama. Moisture conveyor belts are high-altitude atmospheric phenomena known for transporting large volumes of water vapour. 

The researchers proposed in the study that water travels from the tropical Amazon across oceans and mountains to reach the Atacama desert.

According to the study, 40 to 80 per cent of the total precipitation that occurs between the coast and the Andean foothills is associated with moisture conveyor belts.

Local microbial species adapted to dry conditions can be severely affected by rain events related to moisture conveyor belts, the authors noted in the study.

But, the moisture conveyor belts can play an important role in the germination of the blooming desert. For instance, there can be an explosion of colourful wildflowers that occurs in the Atacama every five to seven years, the study said.

The research marks the first time the role of conveyor belts in the Atacama have been catalogued. The scientists examined a 2017 precipitation event that brought more than 50 millimetres of rain to some regions of the Atacama, to figure out the role of moisture conveyor belts and track air masses.

Where Did Most Of The Moisture Originate From?

It was observed that most of the moisture originated in the Amazon basin. This was a surprising result given the high Andes that divide the rain forest from the desert. The researchers discovered that moisture conveyor belts occur throughout the nearby Andes region about four times per year. 

Some of the conveyor belts do not bring much precipitation, while the wettest of the belts can be extreme, the study said.

Quoting Christoph Böhm, the lead author of the study, a statement issued by the American Geophysical Union said that the rain caused by conveyor belts is like a decade worth of rain within one single event within a couple hours. 

The conveyor belts in the midsection of Earth's lowest atmospheric layer, the troposphere, can rain down ten times the annual precipitation. 

The researchers traced how water moves in moisture conveyor belts across the continent, and suggested that the moisture originated in the tropical Amazon basin in the most humid of these extreme events, rather than over the Pacific Ocean that lies west of the desert, the study said.

Further research is required to confidently show that the Amazon is the source of the moisture brought by some of the conveyor belts. 

According to Cornell University geologist Teresa Eileen Jordan, who was not involved in the study, an examination of isotopic data from rain events is necessary to support the idea that the Amazon is the source of the moisture. The isotopic data refers to the atomic chemical information of the rainwater.

She said that the hypothetical path of the water from the Amazon over the Andes would fundamentally change the chemical composition of the water.

New ideas about how water is transported to the Atacama Desert can inform water resource management and predictions of future climate change in the region, the study stated.